Recently, bacteriological researches on periodontal diseases have advanced and, as the results, it has been found that many spirochetes are detected in sites with periodontal diseases and have good correlation with various clinical indices. Further, it has been also found that anaerobic gram negative bacterial are main pathogenic oral microorganisms for periodontal diseases. Among them, Black-pigmented Bacteroides such as Bacteroides gingivalis are particularly noted and many reports about their pathogenicities are present.
Then, attempts are made to detect these pathogenic bacteria in the oral cavity and apply the results to clinical use so that periodontal diseases can be prevented or treated by prognosticating or diagnosing contraction or progress thereof.
However, there are some drawbacks in detection of these pathogenic oral bacteria by a bacteriological method. For example, detection requires highly skilled technique and special equipment such as use of a dark field microscope and handling of anaerobes, and involves complicated operations. Further, it takes a long time and requires skill in cultivation and for analysis of the result. Therefore, there are still difficulties in application to clinical practice.
From the immunological point of view, some attempts are made to detect the presence of the pathogenic microorganisms by determining antibody titer in blood which is humoral immunity to the pathogenic microorganisms, or determining lymphocyte blast formation which is cellular immunity. However, preparation of a specimen requires complicated operations and practical application is still difficult.
Under these circumstances, the present inventors have studied intensively to make detection of the pathogenic oral microorganisms for periodontal diseases applicable to clinical practice possible. As the result, the present inventors have found that some spirochetes in the oral cavity have very specific peptidase-like enzymatic activities and that Black-pigmented Bacteroides such as B. gingivalis, B. intermedius and the like also have similar activities. These can be detected specifically, readily and promptly by a color reaction using particular substrates with precisely reflecting periodontal disease conditions as disclosed in pending patent applications (Japanese Patent Application Nos. 61-179716, 61-233848 and 62-113122).
Separately, the present inventors have found peptidase-like enzyme can be extremely readily and promptly determined using particular compounds which can promote the color development reaction and already filed a patent application (Japanese Patent Application No. 62-286559).